When Cullom resigned after election to the United States Senate, Hamilton became Governor of Illinois.

[1] In 1864, when Hamilton was seventeen years old, he enlisted in the 141st Illinois Volunteer Infantry Regiment during the U.S. Civil War.

[2] Hamilton served for several years as an attorney in Bloomington in a practice with J. H. Rowell until he was elected to the Illinois Senate as a Republican in 1876.

[4] Hamilton was elected Lieutenant Governor of Illinois in 1881, serving under Shelby Moore Cullom.

In 1882, Cullom was elected to the United States Senate and vacated his position as Governor of Illinois the following year.

[4] In 1883, Hamilton sent the Illinois National Guard to quell protests at mines in Madison and St. Clair Counties.

However, after Logan sent a telegram to the convention declining the nomination, Hamilton supported incumbent President Chester A. Arthur.

[2] His 1872 house in Bloomington, Illinois, was recognized with a listing on the National Register of Historic Places on September 6, 1978.